1. Field of the Invention
The present invention generally relates to a method for forming a capacitor in a dynamic random access memory (DRAM) and, more particularly, to a method by deviating the embedded position of the capacitor so as to lengthen the distance between a sidewall portion of the mold cavity and a plug to further increase the mechanical strength of the capacitor and avoid short circuit.
2. Description of the Prior Art
With the rapid development in computer software, a larger memory capacity is required. Since semiconductor processing has reached beyond deep sub-microns, even nanometers, the size of a semiconductor chip becomes smaller. In the case where the semiconductor memory is necessary to have a smaller size with an increased capacity, a high-dielectric material is selected and the surface area of the capacitor is increased. In order to increase the surface area of the capacitor, the capacitor is designed to exhibit a high aspect ratio, which leading to unreliable mechanical strength at the joint at the bottom of the capacitor.
In FIG. 1, which is a cross-sectional diagram of a conventional dynamic random access memory disclosed in U.S. Pat. No. 6,656,785 filed by TSMC. In FIG. 1, an interlayer dielectric layer 11 is formed on a substrate 10 comprising at least a transistor (not shown). The substrate 10 comprises at least a plug 12. The plug 12 is imbedded in a bottom electrode 13 of the capacitor in the interlayer dielectric layer 11 to increase the mechanical strength of the capacitor. However, at the bottom of the capacitor, since the distance between the sidewall portion 14 of the mold cavity and the plug 12 is too short, the dielectric layer 15 and the top electrode 16 are not uniformly deposited at the bottom, leading to short circuit between the top electrode 16 and the bottom electrode 13 to fail a device.
In order to overcome the above mentioned problems, there is need in providing a capacitor in a DRAM by deviating the embedded position of the capacitor so as to lengthen the distance between a sidewall portion of the mold cavity and a plug to further increase the mechanical strength of the capacitor and avoid short circuit.